// Copyright 2015 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

// This is the Android-specific Chromium linker, a tiny shared library
// implementing a custom dynamic linker that can be used to load the
// real Chromium libraries.

// The main point of this linker is to be able to share the RELRO
// section of libcontentshell.so (or equivalent) between the browser and
// renderer process.

// This source code *cannot* depend on anything from base/ or the C++
// STL, to keep the final library small, and avoid ugly dependency issues.

#ifndef BASE_ANDROID_LINKER_LINKER_JNI_H_
#define BASE_ANDROID_LINKER_LINKER_JNI_H_

#include <android/log.h>
#include <jni.h>
#include <stddef.h>
#include <stdlib.h>

// Set this to 1 to enable debug traces to the Android log.
// Note that LOG() from "base/logging.h" cannot be used, since it is
// in base/ which hasn't been loaded yet.
#define DEBUG 0

#define TAG "cr_ChromiumAndroidLinker"

#if DEBUG
#define LOG_INFO(FORMAT, ...)                  \
    __android_log_print(ANDROID_LOG_INFO, TAG, \
        "%s: " FORMAT, __FUNCTION__, ##__VA_ARGS__)
#else
#define LOG_INFO(FORMAT, ...) ((void)0)
#endif
#define LOG_ERROR(FORMAT, ...)                  \
    __android_log_print(ANDROID_LOG_ERROR, TAG, \
        "%s: " FORMAT, __FUNCTION__, ##__VA_ARGS__)

#define UNUSED __attribute__((unused))

// See commentary in crazy_linker_elf_loader.cpp for the effect of setting
// this. If changing there, change here also.
//
// For more, see:
//   https://crbug.com/504410
#define RESERVE_BREAKPAD_GUARD_REGION 1

namespace chromium_android_linker {

// Larger than the largest library we might attempt to load.
static const size_t kAddressSpaceReservationSize = 192 * 1024 * 1024;

// Size of any Breakpad guard region. 16MB is comfortably larger than the
// ~6MB relocation packing of the current 64-bit libchrome.so, the largest we
// expect to encounter.
#if RESERVE_BREAKPAD_GUARD_REGION
static const size_t kBreakpadGuardRegionBytes = 16 * 1024 * 1024;
#endif

// A simple scoped UTF String class that can be initialized from
// a Java jstring handle. Modeled like std::string, which cannot
// be used here.
class String {
public:
    String(JNIEnv* env, jstring str);

    inline ~String() { ::free(ptr_); }

    inline const char* c_str() const { return ptr_ ? ptr_ : ""; }
    inline size_t size() const { return size_; }

private:
    char* ptr_;
    size_t size_;
};

// Return true iff |address| is a valid address for the target CPU.
inline bool IsValidAddress(jlong address)
{
    return static_cast<jlong>(static_cast<size_t>(address)) == address;
}

// Find the jclass JNI reference corresponding to a given |class_name|.
// |env| is the current JNI environment handle.
// On success, return true and set |*clazz|.
extern bool InitClassReference(JNIEnv* env,
    const char* class_name,
    jclass* clazz);

// Initialize a jfieldID corresponding to the field of a given |clazz|,
// with name |field_name| and signature |field_sig|.
// |env| is the current JNI environment handle.
// On success, return true and set |*field_id|.
extern bool InitFieldId(JNIEnv* env,
    jclass clazz,
    const char* field_name,
    const char* field_sig,
    jfieldID* field_id);

// Initialize a jmethodID corresponding to the static method of a given
// |clazz|, with name |method_name| and signature |method_sig|.
// |env| is the current JNI environment handle.
// On success, return true and set |*method_id|.
extern bool InitStaticMethodId(JNIEnv* env,
    jclass clazz,
    const char* method_name,
    const char* method_sig,
    jmethodID* method_id);

// Initialize a jfieldID corresponding to the static field of a given |clazz|,
// with name |field_name| and signature |field_sig|.
// |env| is the current JNI environment handle.
// On success, return true and set |*field_id|.
extern bool InitStaticFieldId(JNIEnv* env,
    jclass clazz,
    const char* field_name,
    const char* field_sig,
    jfieldID* field_id);

// Initialize a jint corresponding to the static integer field of a class
// with class name |class_name| and field name |field_name|.
// |env| is the current JNI environment handle.
// On success, return true and set |*value|.
extern bool InitStaticInt(JNIEnv* env,
    const char* class_name,
    const char* field_name,
    jint* value);

// Use Android ASLR to create a random library load address.
// |env| is the current JNI environment handle, and |clazz| a class.
// Returns the address selected by ASLR.
extern jlong GetRandomBaseLoadAddress(JNIEnv* env, jclass clazz);

// A class used to model the field IDs of the org.chromium.base.Linker
// LibInfo inner class, used to communicate data with the Java side
// of the linker.
struct LibInfo_class {
    jfieldID load_address_id;
    jfieldID load_size_id;
    jfieldID relro_start_id;
    jfieldID relro_size_id;
    jfieldID relro_fd_id;

    // Initialize an instance.
    bool Init(JNIEnv* env)
    {
        jclass clazz;
        if (!InitClassReference(
                env, "org/chromium/base/library_loader/Linker$LibInfo", &clazz)) {
            return false;
        }

        return InitFieldId(env, clazz, "mLoadAddress", "J", &load_address_id) && InitFieldId(env, clazz, "mLoadSize", "J", &load_size_id) && InitFieldId(env, clazz, "mRelroStart", "J", &relro_start_id) && InitFieldId(env, clazz, "mRelroSize", "J", &relro_size_id) && InitFieldId(env, clazz, "mRelroFd", "I", &relro_fd_id);
    }

    void SetLoadInfo(JNIEnv* env,
        jobject library_info_obj,
        size_t load_address,
        size_t load_size)
    {
        env->SetLongField(library_info_obj, load_address_id, load_address);
        env->SetLongField(library_info_obj, load_size_id, load_size);
    }

    void SetRelroInfo(JNIEnv* env,
        jobject library_info_obj,
        size_t relro_start,
        size_t relro_size,
        int relro_fd)
    {
        env->SetLongField(library_info_obj, relro_start_id, relro_start);
        env->SetLongField(library_info_obj, relro_size_id, relro_size);
        env->SetIntField(library_info_obj, relro_fd_id, relro_fd);
    }

    // Use this instance to convert a RelroInfo reference into
    // a crazy_library_info_t.
    void GetRelroInfo(JNIEnv* env,
        jobject library_info_obj,
        size_t* relro_start,
        size_t* relro_size,
        int* relro_fd)
    {
        if (relro_start) {
            *relro_start = static_cast<size_t>(
                env->GetLongField(library_info_obj, relro_start_id));
        }

        if (relro_size) {
            *relro_size = static_cast<size_t>(
                env->GetLongField(library_info_obj, relro_size_id));
        }

        if (relro_fd) {
            *relro_fd = env->GetIntField(library_info_obj, relro_fd_id);
        }
    }
};

// Variable containing LibInfo for the loaded library.
extern LibInfo_class s_lib_info_fields;

} // namespace chromium_android_linker

#endif // BASE_ANDROID_LINKER_LINKER_JNI_H_
